Method and apparatus for controller power train of motor vehicle

ABSTRACT

To provide an engine power-train control apparatus and method for securing both operability and safety by controlling an actual acceleration/deceleration to a target acceleration/deceleration requested by a driver under an undangerous traveling condition and changing the target acceleration/deceleration so as to take precedence of safety traveling if the driver encounters a dangerous traveling condition.  
     To achieve the above mentioned:  
     the control is performed in which acceleration/deceleration and speed of a motor vehicle are detected;  
     a target acceleration/deceleration is operated; a road condition such as a road gradient or presence or absence of a forward motor vehicle is detected to decide whether the road condition is dangerous; and  
     the target acceleration is changed if the condition is decided to be dangerous.

FIELD OF THE INVENTION

[0001] The present invention relates to a motor vehicle control method, particularly to engine power train control apparatus and control method for efficiently controlling an engine power train comprising an engine and a transmission in accordance with information such as a traveling condition to realize an acceleration or deceleration requested by a driver.

BACKGROUND OF THE INVENTION

[0002] As this type of the conventional control method, a method is known which controls at least one of the engine torque adjustment means, transmission gear ratio adjustment means, and braking force adjustment means so that a target acceleration/deceleration requested by a driver become equal to actual motor vehicle acceleration/deceleration as described in the official gazette of Japanese Patent Laid-Open No. 345541/1992.

[0003] In the case of a system for performing control in accordance with only a target acceleration/deceleration requested by a driver like the above prior art, a traffic accident such as crash or speeding may occur if the driver erroneously recognizes a forward traveling condition or too slowly confirms a traveling condition. Moreover, previous confirmation of a road gradient or a corner becomes insufficient and it is difficult to secure a sufficient driving force before entering a slope or corner by controlling a transmission gear ratio.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a control apparatus and a control method capable of controlling an engine power train so that a target acceleration/deceleration requested by a driver becomes equal to an actual acceleration/deceleration under a normal undangerous traveling condition and securing both operability and safety so as to take preference of safety by changing the target acceleration/deceleration if the driver encounters a dangerous traveling condition.

[0005] The above object is achieved by:

[0006] acceleration/deceleration detection means for detecting acceleration/deceleration requested by a driver and motor vehicle speed detection means for detecting a motor vehicle speed;

[0007] target acceleration/deceleration operation means for setting a target acceleration/deceleration in accordance with signals of the acceleration/deceleration detection means and the motor vehicle speed detection means;

[0008] road condition detection means for detecting a traveling road condition including an obstacle such as a forward motor vehicle and dangerous traveling decision means for deciding whether a traveling condition is dangerous or not in accordance with a signal of the road condition detection means; and

[0009] target value change means for changing a target value set by the target acceleration/deceleration operation means when dangerous traveling is decided by the dangerous traveling decision means.

[0010] Acceleration/deceleration detection means obtains an acceleration by detecting a plus-side accelerator stamping distance stamped by a driver and a deceleration by detecting a minus-side accelerator stamping distance moved by the driver so as to release an accelerator and a brake pedal stamping force. Motor vehicle speed detection means uses a signal output from a rotation sensor set to an output shaft or a wheel rotation shaft of a transmission to convert the signal value into a motor vehicle speed. Target acceleration/deceleration operation means operates and sets a motor-vehicle acceleration/deceleration requested by a driver in accordance with the results detected by the acceleration/deceleration detection means and the motor vehicle speed detection means. Road condition detection means detects forward road conditions such as a road curvature radius, road gradient, presence or absence of forward motor vehicle and obstacle, and a road-surface friction coefficient by a camera, radar, navigation map information, and infra-equipment set on a road. Dangerous traveling decision means decides whether the present motor vehicle traveling falls into a dangerous traveling condition several seconds later (this value changes correspondingly to the motor vehicle speed) in accordance with the results detected by the road condition detection means and the motor vehicle speed detection means. Target value change means changes a target acceleration/deceleration when it is decided to be dangerous by the dangerous traveling decision means. Target braking/driving torque operation means operates a target braking/driving torque to be transmitted to a wheel in accordance with the results obtained from road condition detection means, target acceleration/deceleration operation means, motor vehicle speed detection means, and target value change means. Moreover, in accordance with this result, a control input of the following manipulation means is operated. Control input operation means operates a final control input by using a motor vehicle speed, a sufficient driving torque corresponding to the motor vehicle speed, road gradient, target acceleration/deceleration, and target braking/driving torque and considering a fuel consumption, and operability and safety intended by a driver Manipulation means such as engine torque manipulation means, and the transmission gear ratio manipulation means of the transmission, and braking force manipulation means control each control object in accordance with the above operated and detected results.

[0011] As described above, the present invention makes it possible to secure both operability and safety because an actual acceleration/deceleration is controlled to an acceleration/deceleration requested by a driver at the time of traveling under an undangerous condition and safety precedent control is executed during traveling under a dangerous condition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a block diagram of control by an embodiment of the present invention;

[0013]FIG. 2 is a flow chart of control by an embodiment of the present invention, showing the operation by dangerous traveling decision means;

[0014]FIG. 3 is a flow chart of control by an embodiment of the present invention, showing the continuation of FIG. 2;

[0015]FIG. 4 is a flow chart of control by an embodiment of the present invention, showing an operation flow for control of an engine power train;

[0016]FIG. 5 is a flow chart of an embodiment of the present invention, showing the continuation of FIG. 4;

[0017]FIG. 6 is a flow chart of an embodiment of the present invention, showing the continuation of FIG. 4;

[0018]FIG. 7 is a flow chart of an embodiment of the present invention, showing the continuation of FIG. 4;

[0019]FIG. 8 is a conceptual view of a target acceleration table;

[0020]FIG. 9 is an illustration showing a curvature coordinate system of an actual road;

[0021]FIG. 10 is an illustration showing a road curvature coordinate system displayed on an image;

[0022]FIG. 11 is an example of a downward slope;

[0023]FIG. 12 is an example of a upward slope;

[0024]FIG. 13 is an illustration showing a method for detecting a gradient of a forward road;

[0025]FIG. 14 is a block diagram of a system when an embodiment of the present invention is mounted on an actual motor vehicle; and

[0026]FIG. 15 is a flow chart of vibration control by a television camera.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Preferred embodiments of the present invention are described below by referring to the accompanying drawings.

[0028]FIG. 1 is a block diagram of control by an embodiment of the present invention. Acceleration/deceleration detection means 1 detects an acceleration from a plus-side accelerator stamping distance stamped by a foot of a driver and a deceleration from a minus-side accelerator stamping distance moved by the foot of the driver so as to release an accelerator and a brake pedal stamping force. Motor vehicle speed detection means 2 uses a signal output from a rotation sensor set to an output shaft or a wheel rotation shaft of a transmission to convert the signal value into a motor vehicle speed. Target acceleration/deceleration operation means 3 operates and-sets a motor-vehicle acceleration/deceleration requested by a driver in accordance with the results detected by the acceleration/deceleration detection means 1 and the motor vehicle speed detection means 2. Road condition detection means 4 detects forward road conditions such as a road curvature radius, road gradient, presence or absence of forward motor vehicle and obstacle, and a road-surface friction coefficient by such means on the road as a camera, radar, and navigation map information, and moreover, detects signals manipulated by the driver such as a rain-drop sensor signal, headlight signal, and seat belt signal. Dangerous traveling decision means 5 decides whether the present motor vehicle traveling falls into a dangerous traveling condition several seconds later (this value changes correspondingly to the motor vehicle speed) in accordance with the results detected by the road condition detection means 4 and the motor vehicle speed detection means 2. Target value change means 6 changes a target acceleration/deceleration when it is decided to be dangerous by the dangerous traveling decision means 5. Target braking/driving torque operation means 7 operates a target braking/driving torque to be transmitted to a wheel in accordance with the results obtained from road condition detection means 4, target acceleration/deceleration operation means 3, motor vehicle speed detection means 2, and target value change means 6. Moreover, in accordance with this result, a control input of the following manipulation means is operated. Control input operation means 8 operates a control input by using a motor vehicle speed, a sufficient driving torque corresponding to the motor vehicle speed, road gradient, target acceleration/deceleration, and target braking/driving torque and considering a fuel consumption, and operability and safety intended by a driver. In manipulation means 9, engine torque manipulation means, the transmission gear ratio manipulation means of the transmission, and braking force manipulation means are operated in accordance with the above operated and detected results.

[0029] FIGS. 2 to 7 are flow charts of concrete control by this embodiment. FIGS. 2 and 3 are control flows by the dangerous traveling decision means 5. Moreover, various traveling conditions are simultaneously operated in accordance with these flows. First, in processing 10, the following values are read: an FM central frequency f₀ a frequency deviation width ΔF, a triangular-wave repetition frequency f_(m), an increase beat frequency f_(b1), a decrease beat frequency f_(b2), a television camera image, a headlight switch Ls, a rain-drop sensor signal Ws, a seat belt switch Bs, a motor vehicle speed V, and a forward road surface friction coefficient μ. In this case, f₀, ΔF, and f_(m) are generally univocally determined by the type of an FM-CW-system radar (using frequency-modulated continuous wave signal). Therefore, it is possible to previously store the data for each type of radar in a memory. In the case of this system, however, it is necessary to change data and control software when changing radars and thereby, the development man-hour increases. Therefore, it is preferable to use a structure obtained by making a radar intelligent, making the radar output the above signals (f₀, ΔF, and f_(m)), and reading data as described above. In processing 11, a distance between a forward object and this motor vehicle is obtained by using an FM-CW-system radar and the expression described in processing 11. Moreover, a. radio-wave propagation velocity C is equal to 3×10⁸ m/sec and it is previously stored in a memory. In processing 12, a relative speed Vr between the forward object and this motor vehicle is operated by using the expression described in processing 12. The arithmetic expressions in processing 11 and processing 12 are generally-known arts. Processing 13 to processing 19 show a method for a television camera image corresponding to weather and daytime/nighttime. That is, luminances of road images captured correspondingly to weather and daytime/nighttime are different. Therefore, it is necessary to execute road detection corresponding to a luminance and obtain a more accurate road shape. In processing 13, it is decided whether the headlight switch Ls is turned on. When the switch Ls is turned on, that is, Ls equals 1, nighttime is decided and processing 14 is started. In processing 14, it is decided whether the rain drop sensor signal Ws is equal to or more than a constant k1. The constant k1 shows a state in which the road-surface luminance detected by a television camera varies depending on a rain drop, which is previously obtained by actual travel matching and stored in a memory. Therefore, when Ws is equal to or more than k1, processing 15 is started to decide rainy-day nighttime traveling and execute rainy-day nighttime luminance detection and road-surface image processing. In the case of NO in processing 14, cloudless nighttime traveling is decided to execute cloudless nighttime luminance detection and road-surface image processing. Processing 17 is started to execute the same processing as in processing 14. In the case of YES in processing 17, rainy-day daytime traveling is decided to execute rainy-day daytime luminance detection and road-surface image processing. In the case of NO in processing 17, cloudless daytime traveling is decided to execute daytime luminance detection and road-surface image processing. In this case, the road state detection according to luminance detection is a well known art. In processing 20, the forward-road coordinate system processed in processings 15, 16, 18, and 19 is detected by using values showing the coordinates defined in FIGS. 9 and 10. FIG. 9 shows an actual road curvature coordinate system and FIG. 10 shows a road curvature coordinate system obtained by displaying FIG. 9 on an image. Processings 22 and 23 are executed by using the coordinate system. Before processing 22 is executed, a forward road gradient S is detected in processing 21. The gradient S is detected by recognizing the wave lines at the right and left ends of a detected road as shown in FIGS. 11 and 12. For example, a plurality of patterns showing a road shape are stored in a computer capable of performing the operation according to a neutral network and a forward road condition is decided by comparing the patterns with a detected road shape. FIG. 11 shows a downward-slope road shape and FIG. 12 shows an upward-slope road shape. FIG. 13 shows a method for detecting a forward road gradient. An angle γ between right and left lines of a road is detected on the basis of a flat road shape of a television camera image and converted into the road gradient S. When a corner is recognized together with a gradient, they are processed in processings 22, 23. In processing 22, a distance D2 up to the corner is obtained by using the coordinate system shown in FIG. 10 and the following expressions (1) and (2).

y(n+1)/x(n+1)<{(y(1)/x(1)+. . .+y(k)/x(k))/k}  (1)

D2=y(n)  (2)

[0030] At the right side of the expression (1), an averaged linear-line change state is obtained by adding the ratio of Y axis y(n) to X axis x(n) of a linear road shown by a coordinate system up to n=k and dividing the added value by the total k. Then, it is decided whether the next ratio y(n+1)/x(n+1) is smaller than the right side. When the next ratio is smaller than the right side, a value one before n+1, that is, y(n) is substituted for D2 to obtain a distance up to the entrance of the corner. In processing 23, the curvature radius R of the corner is obtained by using the coordinate system shown in FIG. 10 and the following expressions (3) and (4).

m(n)=1(n)  (3)

R=1(n)  (4)

[0031] In the expression (3), it is decided whether X axis 1(n) of the corner road matches Y axis m(n).

[0032] A matched value represents the curvature radius which is obtained by substituting 1(n) or m(n) for R as shown by the expression (4). In this case, the conversion of the distance between X and Y axes is performed by previously storing a correction value between a camera image and an actual distance. Recognition of the above corner can be performed by the same method independently of a change of the road gradient because the camera changes similarly to the motor vehicle body under the present traveling state, that is, on upward, downward, and flat roads. Then, in processing 24, it is decided whether there is other motor vehicle or an object which interrupts traveling ahead. Symbol k2 represents a constant kept within a range capable of measuring a distance up to a forward object by an FM-CW-system radar. That is, it is decided that future traveling is limited by a forward object in the case of YES in processing 24 and that future traveling is limited by a forward corner in the case of NO in processing 24. In the case of YES in processing 24, processing 25 is started to obtain a target motor vehicle speed Vt1 by using the relative speed Vr with a forward object, a function f₂ of the road surface friction coefficient μ obtained from infra-information or the like, and the motor vehicle speed V. Then, in processing 26, an object crash prevention target acceleration Fd1 is operated by using the expression described in processing 26. This expression is calculated by using the following expressions (5), (6), (7), and (8).

T ₁ =W·V ²/2+Ir·(V/r)²/2  (5)

T₂ W·Vt1²/2+Ir·(Vt1/r)²/2  (6)

U(1-2)=T ₁ −T ₂=(½)·{W+(Ir/r ²)}·(V ² −Vt1²)  (7)

Fd 1=U(1-2)/D ₁  (8)

[0033] First, the concept of this processing 26 is to change the present speed V to the future target speed Vt1 in order to secure the safety traveling. The kinetic energy T₁ of a motor vehicle at the initial speed V is shown by the expression (5) and the kinetic energy T₂ of the motor vehicle at the target speed Vt1 is shown by the expression (6). In this case, symbol W represents a motor vehicle weight, Ir represents an inertia moment of a wheel, and “r” represents a wheel radius. A kinetic energy lost from the initial speed to the target speed (T₁−T₂) is equal to a work U (1-2) from the outside {expression (7)}. Therefore, when assuming a distance up to the present point at the present speed V to a point requiring the target speed Vt1 as D1, it is necessary to keep adding a deceleration force Fd1 given by the expression (8) during traveling for the distance D1. Thereby, FD1 is obtained. In the case of NO in processing 24, processing 27 is started and a target speed Vt2 corresponding to R obtained in processing 24 is searched. The speed Vt2 increases as R increases. That is, it is possible to increase a target speed as R increases. Moreover, it is necessary to decrease Vt2 as “μ” obtained from the infra-information decreases in order to secure the safety. In processing 28, the same processing as in processing 26 is executed to operate a target deceleration force Fd2 for preventing speeding at a corner. After processings 26 and 28, processings 29 and 34 shown in FIG. 3 are started respectively. In processing 29, it is decided whether the seat belt switch Bs is turned on. In this case, it is purposed to change motor vehicle deceleration states for avoiding encounter with a dangerous state by keeping the present motor vehicle speed in accordance with the fact of driver's wearing a seat belt or not. In the case of YES in processing 29, that is, when a driver wears a seat belt, processing 30 is started to decide whether the target deceleration Rd1/W (force/weight) is k3 or more. The value k3 is a safety deceleration constant in which a driver does not have a sense of incongruity when wearing a seat belt. In the case of YES in processing 30, processing 31 is started to substitute “1” for a dangerous traveling flag (there is an object ahead) FlgCar for warning that a driver will feel uncomfortable at the present speed and dangerous deceleration will occur. Control operations to be mentioned later shown from FIG. 4 to FIG. 7 are executed by using the flag signal. In the case of NO in processing 30, processing 33 is started to substitute 0 for FlgCar. In the case of NO in processing 29, processing 32 is started to decide whether a safe deceleration can be obtained without a sense of incongruity even if a driver does not wear a seat belt. In the case of YES in processing 32, processing 31 is started. In the case of NO in processing 32, processing 33 is started. A value k4 is a safe deceleration constant in which a driver does not have a sense of incongruity in wearing no seat belt. Moreover, in processings 34 to 38, processings same as the above are executed. In this case, if it is decided before entering a corner that a driver will feel uncomfortable and a dangerous deceleration will occur when entering the corner, the value “1” is substituted for a flag FlgCor. Moreover, it is possible to obtain the setting of the target speed Vt2 for the road curvature radius R of processing 27 from the following expression (9).

Vt2=k 20·{square root}{square root over (μ)}·R·g  (9)

[0034] Where,

[0035] g: Gravitational acceleration

[0036] k20: Constant for correction of center of gravity of vehicle

[0037] As for the value “μ”, for example, 0.8 represents a dry asphalt road, 0.5 represents a wet asphalt road, and 0.3 represents a snow-covered road. Therefore, it is necessary to store a target speed, that is, a corner traveling limit speed for each value of “μ” in a memory. Moreover, it is possible to perform operation by using the expression (9) at any time. Furthermore, these values are changed depending on the center-of-gravity position of a motor vehicle. Therefore, it is necessary to change a constant value for each type of motor vehicle. For example, a one-box car which is unstable because of a high center-of-gravity position has a small value of k20.

[0038] FIGS. 4 to 7 show a flow chart for engine power-train control according to the above traveling condition. In processing 40 of FIG. 4, the following values are read: an accelerator stamping distance α, a brake stamping force β, a motor vehicle speed V, a forward road gradient S obtained above, a distance D1 up to a forward object, dangerous traveling flags FlgCar and FlgCor, a forward road surface friction coefficient μ, target deceleration forces Fd1 and Fd2, and an engine speed Ne. In processing 41, the value of a target acceleration/deceleration Gt is searched which is a function of α and β set as shown in FIG. 8. FIG. 8 is a conceptual view of a target acceleration/deceleration table. In FIG. 8, the continuous line represents the time of acceleration, that is, a case in which the present read value becomes larger than the last accelerator stamping distance (read value one cycle before in the operation flow) and the broken line represents the time of deceleration, that is, a case in which the present read value becomes smaller than the last accelerator stamping distance (read value one cycle before in the operation flow). Moreover, a plurality of the above values are set in accordance with various motor vehicle speeds as shown in FIG. 8. FIG. 8 shows only ranges. Furthermore, to keep the motor vehicle speed constant (auto cruise control), a target acceleration is set to 0 in an area where the accelerator stamping distance is not 0 but small as shown by a one-dot chain line. Thereby, it is possible to keep the present motor vehicle speed after acceleration. In FIG. 8, the time of acceleration and the time of deceleration are shown by one drawing. Actually, however, when showing a case in which the accelerator stamping distance is plus by the right top area and a case in which the accelerator stamping distance is minus by the right bottom area, two tables are necessary for the time of acceleration and the time of deceleration. Moreover, it is possible to realize the time of acceleration and the time of deceleration by one table in order to reduce a memory capacity. In this case, however, the accelerator stamping distance is slightly fluctuated due to motor vehicle vibrations though a driver requests a constant acceleration and thereby, torque fluctuation may occur. Therefore, it is necessary to add new hysteresis means. Then in processing 42, it is decided whether the dangerous traveling flag FlgCar for deciding whether a traveling condition in which a driver feels uncomfortable occurs in future because of an object such as a motor vehicle present ahead is set to 1. In the case of NO, processing 43, started to decide whether the dangerous traveling flag FlgCor for deciding whether a traveling condition in which a driver feels uncomfortable occurs in future because of a corner present ahead is set to 1. In the case of NO in processing 43, processing 44 is started to operate a target braking/driving torque Tot by using the target deceleration Gt obtained in processing 41 requested by a driver and the following expression (10) described in processing 44.

Tot=r·(W+Wr)·Gt/g+μr·W+μl·A·V ² +W·sinS  (10)

[0039] Where

[0040] r: Wheel radius,

[0041] W: Motor vehicle weight,

[0042] Wt: Rotation equivalent weight,

[0043] g: Gravitational acceleration,

[0044] μr: Rolling resistance coefficient,

[0045] μl: Air resistance coefficient,

[0046] A: Forward projection area

[0047] In the right side of the expression (10), the first term represents an acceleration torque necessary for motor vehicle acceleration, the second term represents a rolling resistance, the third term represents an air resistance, and the fourth term represents a grade resistance. In this case, Gt, V, and S are determined by the above described flow and constants determined for each motor vehicle are previously set to variables other than Gt, V, and S. In the case of YES in processing 43, it is decided that there is a corner ahead and deceleration is necessary and processing 45 is started. In processing 45, it is decided whether the target acceleration/deceleration Gt requested by the driver in processing 41 are equal to or less than the target deceleration Fd2/W decided from the present traveling condition. In the case of YES, the driver decides that he (or she) makes a correct decision that dangerous traveling occurs in future and processing 44 is started. In the case of NO, because correct decision cannot be made, the target acceleration/deceleration is rewritten to the target deceleration Fd/2 judging from a traveling condition in processing 46 and processing 44 is started. When YES is decided in processing 42, processing 47 is started to decide whether the present motor vehicle speed V is, for example, 15 km/h or less. This is because a distance up to a forward object must be controlled instead of control of a target acceleration/deceleration in the case of a low motor vehicle speed such as the time of a traffic jam or the time of parking a motor vehicle in a garage. Therefore, in the case of NO in processing 47, processing 48 is started to control the target acceleration/deceleration. In the case of YES, processing 49 is started to control a target distance. In processings 48 and 50, the same processings as in processings 45 and 46 are performed and processing 44 is started. In processing 49, it is decided whether the distance D1 up to a forward object is equal to or less than a limit value k8. The value k8 represents, for example, approx. 1 m which is the minimum distance to avoid the crash with the forward object. In the case of YES in processing 49, that is, in the case of just before the crash, processing 51 is started to set the target motor vehicle speed Vt to 0. Then, in processing 52, a constant k10 in which a motor vehicle can stop at a low motor vehicle speed is input to a target brake Bp. In the case of NO in processing 49, processing 53 is started to decide whether α is larger than 0.

[0048] In the case of YES, processing 54 is started to input a constant value k9 to the target acceleration/deceleration. The value k9 is a target acceleration value for the safety first at a low motor vehicle speed when an object is present ahead. Thereby, for example, even if a driver erroneously stamps an accelerator, safety traveling can be secured because a motor vehicle travels at a constant acceleration. Moreover, though a constant acceleration is set in the above case, it is also possible to maximize the value k9 and adjust the maximized k9 to the target acceleration/deceleration Gt when the value k9 exceeds the maximum value. Then, processing 55 is started to operate the target braking/driving torque Tot similarly to the case of processing 44. Then, in processing 56, a target engine torque Tet is operated in accordance with the expression using a present transmission gear ratio (e.g. speed 1 because of 15 km/h or less), a torque ratio t(e) obtained from a torque converter speed ratio “e”, and Tot described in processing 55. In processing 57, a target engine speed Net to be used for a later processing (for calculating a target throttle opening degree and a target braking force) is obtained by assuming the Net equals a detected engine speed Ne. After processings 52 and 57, processing 58 shown in FIG. 7 is started to search a table of the target engine torque Tet corresponding to the X-axis target engine speed Net and obtain a target throttle opening degree θ, a target transmission gear ratio i, and the target braking force Bp. When starting with processing 52, the target braking force Bp shown by a white circle in processing 58 in FIG. 7 is searched to obtain the target throttle opening degree=0 and the target transmission gear ration i=speed 1. Then, processing 59 is started to output i, θ, and Bp. When starting with processing 57, a target throttle opening degree θ shown by a black circle in FIG. 7 is searched to obtain the target braking force Bp=0 and the target transmission gear ratio i=1. Then, processing 59 is started. After processing 44 in FIG. 4, processing 60 is started to decide whether the forward road gradient S obtained in FIG. 2 is larger than k5. The value k5 is a constant for an upward slope gradient, which makes it possible to control a speed change point for reduction of fuel consumption in which a driver does not have a sense of incongruity even if a high motor vehicle speed is changed when a traveling load is relatively large.

[0049] In the case of YES in processing 60 in FIG. 4, fuel consumption speed change is executed, processing 61 shown in FIG. 7 is started, and a torque-converter output shaft torque for each transmission gear ratio, a so-called turbine torque Tt(n) is operated. The value “n” of Tt(n) depends on a transmission set to a motor vehicle. It is preferable to set “n” to 4 in the case of a four-speed transmission and to a controllable value such as 20 in the case of a non-stage transmission. The torque Tt(n) is obtained by dividing the above Tot by “n” transmission gear ratios gr(n). In processing 62, a torque-converter output-shaft speed for each transmission gear ratio, that is, a turbine speed Nt(n) is operated The speed Nt(n) is obtained by multiplying the above V by “n” transmission gear ratios. In processing 63, a reverse pump capacity coefficient cn(n) for each transmission gear ratio is operated by using the Tt(n) and Nt(n) obtained in processings 61 and 62. In processing 64, a speed ratio e(n) for each transmission gear ratio is searched. In this case, the relation between cn(n) and e(n) can be obtained by using the following expressions (1), (12), and (13).

e=Nt/Ne  (11)

Tt=t·c·Ne ²  (12)

cn(n)=(t·c/e ²)=Tt/Nt ²  (13)

[0050] where,

[0051] e: Torque-convert input/output shaft speed ratio

[0052] Nt: Torque-converter output shaft speed

[0053] Ne: Engine speed

[0054] Tt: Torque-converter output shaft torque

[0055] t: Torque-converter torque ratio (Function of “e”)

[0056] c: Torque-converter pump capacity coefficient (Function of “e”)

[0057] In processing 65, a torque ratio t(n) for each transmission gear ration is obtained as a function of the speed ratio e(n). In processing 66, the target engine torque Tet is operated by using the Tt(n) and t(n) obtained in processings 61 and 65. In processing 67, the target engine speed Net is operated by using the Nt(n) and e(n) obtained in processings 62 and 64. Moreover, in processing 68, the speed change ratio “i” for the minimum fuel consumption is obtained by using a value for transmission gear ratio obtained in processings 66 and 67. In this case, it is shown that “n” is equal to 4 (four-speed transmission). In the case of fuel consumption comparison here, the power horse of the transmission output shaft is changed due to slip of the torque converter. Therefore, a table of fuel consumption is used which can detect a torque converter efficiency and an engine efficiency at the same time. In processing 69, a target throttle opening degree θ table to be set with the same shaft as that in processing 68 is searched to obtain θ at the same position as that of the speed change ratio “i” obtained in processing 68.

[0058] In the case of NO in processing 40 in FIG. 4, processing 70 is started to decided whether the forward road gradient S is smaller than −k6. The value −k6 is a constant for a downward gradient. In the case of a gradient smaller than the value −k6, fuel cut is executed to reduce fuel consumption only when a driver requests deceleration. Whether the driver requests deceleration is decided in processing 71 Therefore, it is decided whether the target acceleration/deceleration Gt is equal to or less than the deceleration constant k7. In the case of YES, processing 72 shown in FIG. 5 is started to operate a target engine torque Tet for each transmission gear ratio by using Tot and gr(n). In this case, torque converter characteristics are not considered because the slip of a torque converter almost comes to zero and the input/output shaft speed ratio of the torque converter comes to 1 in the case of deceleration. In processing 73, the target engine speed Net is operated by using the above motor vehicle speed V and gr(n) similarly to the case of processing 72. In the case of deceleration control, it is necessary to instantaneously obtain a sense of acceleration requested by a driver in acceleration after deceleration. Therefore, it is necessary to set a target sufficient driving torque Tst at the time of deceleration and the torque Tst is obtained in processing 74. The torque Tst is set correspondingly to the motor vehicle speed V, which can be changed in accordance with the taste of the driver. For example, when V is small, Tst increases because a speed change ratio is set to the low side. Then, in processing 75, a sufficient engine torque Tes(n) for each transmission gear ratio is obtained from a table comprising Tet and Net. In processing 76, a sufficient driving torque Ts(n) when changing speed change ratios under the present traveling state is operated by using the Tes(n) and gr(n) obtained in processing 75. In processing 77, the results obtained in processings 74 and 76 are compared to obtain a target speed change ratio “i” where Ts(n) larger than Tst and closest to the Tst, a target throttle opening degree θ, and a target braking force Bp. Then, processing 59 shown in FIG. 7 is started.

[0059] In the case of NO in processings 70 and 71 in FIG. 4, a routine at the time of flat road traveling including a corner and downward slope acceleration is formed. In processing 78, a target sufficient driving torque Tst requested by the driver is searched similarly to the case of processing 74. Then, processing 79 shown in FIG. 6 is started to decide whether the above Tot is smaller than 0. When the Tot is smaller than 0, deceleration is decided and processing 80 is started. Because of deceleration control from processing 80, processings 80, 81, 82, 83, and 84 are execute the same processings as in processings 72, 73, 75, 76, and 77 respectively and then, processing 59 in FIG. 7 is started. When it is decided in processing 79 that Tot is equal to or more than 0, that is, NO is decided, a target engine torque Tet and engine speed Net considering torque converter characteristics are calculated. Processings 85, 86, 87, 88, 89, 90, and 91 execute the same processings as in the above processing 61, 62, 63, 64, 65, 66, and 67 respectively and then, processing 82 is started.

[0060]FIG. 14 shows a system block diagram when mounting an embodiment of the present invention on an actual motor vehicle. An engine 93 and a transmission 94 are mounted on a chassis 92, where throttle opening degree (or air flow rate) θ, fuel quantity, ignition timing, braking pressure, and transmission gear ratio are controlled in accordance with signals output from an engine power-train control unit 95. Fuel control uses the inlet-port injection system widely used at present or cylinder injection system with a high controllability. Moreover, a television camera 96 for detecting an outside state and an antenna 97 for detecting infra-information are mounted on the chassis 92. An image of the television camera 96 is input to a traveling condition discrimination unit 98 and processed to recognize a road gradient, corner curvature radius, traffic light information, and traffic sign. Moreover, an FM-CW-system radar 102 is set at the front of the chassis 92 to detect a distance up to a forward motor vehicle or object and a relative speed. Furthermore, the antenna 97 connects with an infra-information terminal 99, a forward road state (wet road, dry road, or snow-covered road, or presence or absence of sand on a road) is detected in accordance with infra-information, and the traveling condition discrimination unit 98 operates a road-surface friction coefficient μ. Moreover, a traveling condition can be discriminated in accordance with map information stored in a CD-ROM 100 or the like and forward road states (e.g. gradient and corner curvature radius) can be detected. A signal corresponding to a traveling condition, a degree of risk on the traveling condition, and a road-surface friction coefficient μ are output from the traveling condition discrimination unit 98 and input to the engine power-train control unit 95. A throttle opening degree θ, fuel quantity, ignition timing, transmission gear ratio i, and braking force Bp by a braking-pressure control actuator 103 are controlled in accordance with the signal Moreover, an accelerator stamping distance α, brake stamping force β, motor vehicle speed V, engine speed Ne, rain drop signal Ws, seat belt switch Bs, and headlight switch Ls are input to the engine power-train control unit 95 and used for the control operations shown in FIGS. 2 to 7. Furthermore, an acceleration sensor 104 for detecting, for example, a vertical acceleration is set to the television camera 96 and an actuator 101 for restraining and controlling vibrations is set to the bottom of the television camera 96 to feedback-control a signal output from the acceleration sensor 104 and prevent the detection accuracy of the television camera 96 from deteriorating due to oscillation of the camera.

[0061]FIG. 15 is a control flow chart for restraint of vibrations of the television camera 96. First, a signal Gs output from the acceleration sensor 104 set to a chassis or television camera is read in processing 110. Then, the signal Gs is integrated to operate a motor vehicle fluctuation speed Vtd in processing 111. Moreover, in processing 112, the operated value of the Vtd is integrated to operate a vertical fluctuation position (that is, a stroke) Std of the motor vehicle. Then, in processing 113, it is decided whether the Std equals a constant k15 representing a constant television-camera image detection angle. When the Std equals the constant k15 in processing 113, processing 114 is started to substitute the last driving signal As_((n−1)) for a control signal As_((n)) for driving the actuator 101 which controls a television-camera angle and then, processing 115 is started. In processing 115, the present driving signal As_((n)) is substituted for the last driving signal As_((n−1)) and returned. In the case of NO in processing 113, that is, when it is decided that the Std is not equal to the constant k15, processing 116 is started to obtain a deviation AS between the Std and the constant k15 and then, processing 117 is started. In processing 117, a value obtained by adding a PID control value of the ΔS to the last driving signal As_((n−1)) for the As_((n)) and then, processing 115 is started. Thus, it is possible to restrain detection errors of a road gradient and road curvature radius due to oscillation of a television camera and accurately control a power train. Moreover, it is possible to use a suspension control sensor used for chassis vibration restraint as the acceleration sensor 104 in order to reduce costs.

[0062] As described above, the present invention has an advantage that fuel profitability, operability, and safety can be improved because an actual acceleration/deceleration can be controlled to an acceleration/deceleration requested by a driver at the time of traveling under an undangerous condition. 

What is claimed is:
 1. An apparatus for controlling a power train of a motor vehicle, comprising: acceleration/deceleration detection means for detecting a motor vehicle acceleration/deceleration requested by a driver and motor vehicle speed detection means for detecting a motor vehicle speed; target acceleration/deceleration operation means for setting a target acceleration/deceleration in accordance with signals output from the acceleration/deceleration detection means and the motor vehicle speed detection means; road condition detection means for detecting a road condition at the time of traveling including an obstacle such as a forward motor vehicle; dangerous traveling decision means for deciding whether a traveling conditions is dangerous or not in accordance with a signal output from the road condition detection means; and target value change means for changing target values set by the target acceleration/deceleration operation means when dangerous traveling is decided by the dangerous traveling decision means.
 2. The apparatus for controlling a power train of a motor vehicle according to claim 1 , further comprising: target braking/driving torque operation means for operating a braking/driving torque to be transmitted to a wheel in accordance with a road condition obtained by at least the road condition detection means; control input operation means for operating control inputs of an engine, transmission, and brake in accordance with at least the target braking/driving torque; and control means for controlling at least one of the torque manipulation means of the engine, transmission gear ratio manipulation means of the transmission, and braking force manipulation means of the brake.
 3. The apparatus for controlling a power train of a motor vehicle according to claim 1 , wherein: the dangerous traveling decision means has means for detecting a seat-belt working state and changes reference values for dangerous-traveling decision setting in accordance with the working state.
 4. The apparatus for controlling a power train of a motor vehicle according to claim 1 , wherein: the target value change means has low motor vehicle speed decision means for deciding whether a signal obtained by the motor vehicle speed detection means shows a low motor vehicle speed and limits the maximum target acceleration/deceleration when the present motor vehicle speed is decided as the low motor vehicle speed.
 5. The apparatus for controlling a power train of a motor vehicle according to claim 1 , wherein: the target acceleration/deceleration operation means has two tables for acceleration and deceleration respectively.
 6. The apparatus for controlling a power train of a motor vehicle according to claim 5 , wherein: the target acceleration and deceleration table for deceleration has at least two target acceleration/deceleration zero areas for a signal of the acceleration/deceleration detection means for motor vehicle speed constant control.
 7. The apparatus for controlling a power train of a motor vehicle according to claim 1 , wherein: the road condition detection means detects forward road conditions by a television camera and a radar, and detects a road gradient and a road curvature radius in the case of the detection by the television camera and a forward object in the case of the detection by the radar.
 8. The apparatus for controlling a power train of a motor vehicle according to claim 2 , further comprising: means for deciding the degree of the detected road gradient in the control input operation means; means for setting a target sufficient driving torque in accordance with the above decision result; and means for comparing fuel consumption values to execute the control for the minimum fuel consumption.
 9. The apparatus for controlling a power train of a motor vehicle according to claim 8 , wherein: vibrations of the television camera are restrained by acceleration detection means and vibration restraint and control means.
 10. A method for controlling a power train of a motor vehicle, comprising the steps of: detecting a motor vehicle acceleration requested by a driver; detecting a motor vehicle speed; setting a target acceleration/deceleration in accordance with the detected acceleration/deceleration and the detected motor vehicle speed; detecting a road condition during traveling including an obstacle such as a forward motor vehicle; deciding whether the present motor vehicle traveling condition is dangerous in accordance with the detected road condition; and changing the target acceleration/deceleration when the present motor vehicle traveling condition is decided to be dangerous.
 11. The method for controlling a power train of a motor vehicle according to claim 10 , further comprising the steps of: operating a target braking/driving torque to be transmitted to a wheel in accordance with the detected road condition; operating a torque of an engine, a transmission gear ratio of a transmission, and a control input of a brake in accordance with the target braking/driving torque; and controlling at least one of the torque of the engine, the transmission gear ratio of the transmission, and the brake.
 12. The method for controlling a power train of a motor vehicle according to claim 10 , further comprising the steps of: detecting a seat-belt working state; and changing criteria for deciding whether the traveling condition is dangerous in accordance with the working state.
 13. The method for controlling a power train of a motor vehicle according to claim 10 , wherein: the target acceleration of the target acceleration/deceleration is changed by deciding whether the detected motor vehicle speed is low and the maximum change value of the target acceleration/deceleration is limited when the motor vehicle speed is decided to be low.
 14. The method for controlling a power train of a motor vehicle according to claim 10 , wherein: the target acceleration/deceleration is set in accordance with two previously prepared tables for acceleration and deceleration respectively.
 15. The method for controlling a power train of a motor vehicle according to claim 14 , wherein: the table for deceleration has at least two target acceleration/deceleration zero areas for the detected acceleration/deceleration for motor vehicle speed constant control..
 16. The method for controlling a power train of a motor vehicle according to claim 10 , wherein: a forward road condition is detected by a television camera and radar in the case of the road condition detection: a road gradient and a road curvature radius are detected in the case of the detection by the television camera; and a forward object is detected in the case of the detection by the radar.
 17. The method for controlling a power train of a motor vehicle according to claim 11 , wherein: the control input operation decides the degrees of the road gradient in the detected road condition; a target sufficient driving torque is set in accordance with the decision result; fuel consumption values for the degree of the road gradient and the target sufficient driving torque are obtained and compared; and at least one of the engine torque, the transmission gear ratio of the transmission, and the brake is controlled in accordance with the comparison result so that fuel consumption is minimized. 